This invention relates to a sputtering type of metal ion source utilizing the electron confining method of PIG (Penning Ionization Gauge) which can be used for an ion beam deposition, an ion implantation, and the like.
It is necessary to supply metal particles to an ion generating chamber when producing metal ion beams. Generally known methods of producing the metal ion beams inclue sputtering and vaporization. In the case of a refractory metal, the method of utilizing sputtering is adopted with advantage, and moreover ion beams of the refractory metal can be comparatrvely easily produced when utilizing the sputtering type of an ion source. For example, according to "N. Angert, R. Keller, and M. Miller: Proc. Int'l Ion Engineering Congress ISITAT '83 & IPAT '83, Kyoto (1983), p. 225.", the conventional sputtering type of the ion source is constructed as shown in FIG. 1. This is the sputtering type of a duo-plasmatron ion source made by the combination of the techniques of arc discharge and sputtering.
In FIG. 1, an auxiliary gas such as argon (Ar) is introduced into a cathode chamber 2 through a gas introducing hole 1, and then, arc discharge is generated between a cathode filament 3 and an anode 4. A material to be ionized is placed at a portion of a sputtering electrode 6 to which a negative voltage is applied in an anode chamber 5. When ions generated by the arc discharge flow from the region of the cathode filament 3 to the anode 4, the ions bombard the sputtering electrode 6 having a negative potential, and then, the material is sputtered. The sputtered neutral particles are ionized in the plasma, and taken out by means of an electrode 7 for taking out the ionized material. An intermediate electrode 8 and the anode 4 are made of mild iron so as to form a magnetic path, and a strong axial direction magnetic field, i.e. 10.sup.3 to 10.sup.4 gausses, is formed between two electrodes (the intermediate electrode 8 and the anode 4) by a magnetic coil 9 so that the plasma is concentrated in the vicinity of a small aperture of the anode 4 and the ionization rate is improved. Although the mixtures of the ions of the material desired to be ionized and the ions of an auxiliary gas are obtained, these ions are filtrated by a mass separator after they are taken out as ion beams. Numeral 10 denotes a coolant.
However, in the above-mentioned structure, there are problems as described below. The pressure of gas in the ion source is high such as 10.sup.-2 to 10.sup.-1 Torr, and the degree of vacuum of an ion transporting chamber is poor such as 10.sup.-4 Torr. Besides, as a filament is used, the lifetime is short such as 6 to 30 hrs. Moreover, ions are gathered in the vicinity of a central axis by the strong magnetic field so that the sputtering electrode is not sufficiently bombarded.